Method of conditioning electrodes



JIanJG. 1925': 1,522,143

R. B; RATHBUN METHOD OF CONDITIONING "ELECTRODES Filed June 5, 1921 2Sheets-Sheet I.

avwemtoz Jan. 60 R. B. RATH'BuN 7 METHOD OF CONDITIONING ELECTRODESFiled Jun e :5, 1921 2 Sheets-Sheet 2 lllllll I l I I I I I U fiu El-INVENTOR Boss film/"Z010 [Edi/Maia ATTORNEY atented .tan. 6, 1925 ROSSBUXTON RATHBUN, OF SALT LAKE ING AND REFINING COMPANY, OF

JERSEY.

CITY, UTAH, ASSIGNOR TO AMERICAN SMELT- NEW YORK. N. Y., A CORPORATIONOFNEW METHOD OF CONDITIONING ELECTRODES.

Application filed June 3,

To all whom it may concern:

Be it known that 1, Ross BUXTON RATH- BUN,

a citizen of the United States, and resident of Salt Lake City,

in the county of 5 Salt Lake and State of Utah, have invented certainnew and useful Improrements in Methods of Condi tioning Electrodes, of

tality for carrying out the method.

It is understood that in the practicing of this method of ele ctricprecipitation, the

solid, precipitated matter especially when dry has a tendency trodes andas 1t has to collect on the elee high dielectric strength it acts toinsulate the electrodes, automatically reducing the value below whatcurrent strength to :1 1s required. Numerous attempts have been made toremedy this defeet, among which might be mentioned that it has beensuggested to moisten the gases carrying the particles or eipitate'dparticles or acid as they come trodes. These meth to moisten theprethemselves with water in contact with the elecods however, use. uptoo much acid to be economical; the acid and water both act todeteriorate. the apparatus, and the cooling of the gases effects thenatural draft through the discharging stacks.

Again it has been suggested to wet the electrodes themselves with acontlnuous stream of water but this gi ves rise to a slimy precipitatewhich cannot be readily handled.

Accordingly, one

of the objects of the invention is to provide a simple method foreffecting a constant,

complete precipitation of the solids from the gases and in which methodpractically all of the solids are precipitated in a dry, readilyhandleable condition and, of most wde a method which inexpensively.

I attain this inve treating the actlve serious import, to prowill attainthese results ntion by intermittently faces of the electrode,

while not in active operation, 'or while 1n ac- .tive operatlon, w th athin film or rather mist of a readily diifuslble conducting liquid suchas sulph So treating the e uric acid. lectrodes has the effect 1921.Serial No. 474,798.

of elin'iinating the disadvantages in the prior methods, except possiblycorrosive actions, but the use of acid of high concentration usuallyabout 136., minimizes any acid reaction especially as the parts areprotected somewhat by the dry dust coating.

It is apparently necessary for the successful operation of this methodthat the acid be applied uniformly over the electrode sur faces in theform of finely divided particles. and therefore one of the objects ofthe apparatus features of this disclosure is toproride a'simple form ofapparatus which will condition all of the electrodes with the sameamount of acid applied in substantially the same cloud-like mist, forthe wetting of any electrode with too much acid acts so as to require alower voltage than is desirable. to prevent sparking over at theelectrodes.

It is sometimes more convenient to. apply the cloud of acid mist to theelectrodes by introducing it with the gas periodically, just before itpasses through the'electrodes, the mist being precipitated with thedust, but the fact that the gas or smoke is there is incidental ratherthan necessary, but in so far as the method feature of the disclosure isconcerned the electrodes are initially treated during the period whenthere is no gas flow-with an atomized cloud of concentrated sulphuricacid G06(l Be. applied to the electrodes for a period of about a halfminute or until all parts thereof are presumably covered withclosely-positioned, minute drops but not so copiously applied as tocause anything in the nature of streams or a running'coating of anynature. The mist is carried into contact with the electrodes by means ofa current of air produeed by the draft or pull of the chimney. The gasfrom which the solid matteris to be precipitated is then passed throughthe electrostatic field formed by the energized electrodes in the mannerwhich is well known in the practicing of the Cottrell method. The solidsare precipitated from the gases; the gases pass from the electrostaticfield practically clear, and this clearing of\the gases will continueuntil the effect of the acid becomes dissipated. The flow of gas is theninterrupted; all of the precipitate possible shaken from the electrodesto enable the acid mist to contact with the electrode itself rather thanthe precipitated turned on coat of dust, the electrodes are againtreated to an acid mist; the gas is again and the operation repeated. Ausual practice is to treat the electrodes once every twenty-four hoursbut this period may vary from a much shorter period to a longer one,depending on the amount of solid matter suspended in the gas, itsdryness and the amount of matter present, such as lime or compounds ofzinc, which have a tendency to neutralize the acid.

While the present disclosure features the spraying of the electrodeswith an atomized mistof the acids, it is to be understood that thismethod of handling the conditioning liquids is largely to featureeconomy in the amount of .material used and it is sug gested that theacids might be otherwise applied as by painting the electrodes provided,of course, that the acids were not thickly applied or applied in anyother way which might interfere with the necessary electric conditions.

Sulphuric acid has been suggested due to its relative cheapness overother suitable treating liquids; due to the fact that it is extremelydivisible; due to its high boiling point; due to its high rate ofdiffusion over matter and due to the fact that it breaks up into threeextremely mobile hydrogen radicals. It is, however, suggested that othertreating materials might be used and for an illustration of one suchmaterial reference is made to nitric acid.

Referring to the apparatus features of the disclosure reference is madeto the ac c'ompanying drawings of two forms of electrode treatingapparatus, suitable for use in practicing the method herein featured.Figure 1 is a diagrammatic view of a screen type of treater in which theupper part is shown in plan and the lower part in eleva-' tion. Figure 2is a similar view of a treater of the pipe type and Figures 3 and 4 areeach enlarged transverse views of the dis-- tributing pipe shown inFigure 2 and taken 7 respectively on the lines 3-3 and 4--4 of thefigure.

Referringspecifically to the showing in Figure 1 there are shown gasconducting conduits or flues 10 and 11, through which the gases passhorizontally and in which are hung a plurality of electrodes 12 and 13electrically connected so as to precipitate the dust from the gas fumespassing through the flue in the manner well-known in connection with theoperation of electrolytic precipitation in the screen typeof treater.

The discharge electrodes which are in the form of wires, are hung fromsupporting pipes 14, which pipes have heretofore been in the form ofconducting rods for leading the electric current to the electrodes butwhich, in this instance, are in the form of pipes provided with a seriesof closely positioned small vents, 15, opening downwardly for thepurpose of distributing the atomized acid as hereinafter more fullydescribed.

The assive or rounded electrodes which pressure is introduced to aslarge a number of points as is possible and in this way the pressure iskept fairly uniform over the entire system. For this purpose the acidinlet, 29, discharges into a main pipe, 16, of

relatively large conducting capacity, which pipe, 16, branches in twoways and discharges into a plurality of distributing header pipes, 17,18and 19, the latter of which is positioned within the outline of a gasconduit and discharges directly into the set of spraying pipes, .14,located in the gas conduit. In so far as is possible each set of pipescollectively has a conducting capacity equal to the conducting capacityof the pipe which supplies the set so as to insure uniform velocity ofthe mist, thus keeping it in suspension in the several branches andpreventing any of it from settling out in droplets as would be the caseif the mist has too slow' a velocity due to too large a pipe.

It is necessary to connect the main pipe to the supply system simplyduring the time when it is required to condition the electrodes andwhile the electric precipitating features of the device arefunctioningit is necessary to insulate the structure from the conditioning system.This is most readily eifected by disconnecting the part of conditioningpiping exteriorly of the system from the part within the gas conduit andone means for effecting this is to make a part of the piping, such asthe part shown at 20, in the form of a short length of pipe connected bymeans of two unions which can-be readil broken.

In this system it s required that air in large volume, and preferablydry, be supplied to the atomizing device and for this purpose there isdisclosed an-approved form of air charging conduit including, in order.a source of air under compression indicated by the supply pipe 21. Thisleads to a moisture trap, 22, and from the moisture trap through an airdryer, 23, from which the dried air is discharged into an air storingreceptacle. 2%. From the air storing receptacle, 24. the air isdischarged through a system of relatively large air supplying pipes, 25,leading to the several atomizing devices supplied from this air source.

The acid is supplied to'the atomizer from an acid supply tank, 26,through a conducting pipe, 27, which leads past the control valve, 28,to a spray nozzle, 29. having a perforated head, 30. and facing in thedirection of air flow through the vaporizer as is well-known in devicesof this character. It is not essential that the device, 29, act. as anatomizer but may serve only as a means of conveying the acid into theair stream, the atomization taking place at the small orifices. I

Air pressure is maintained on the acid level in the tank, 26, from asource of air supply indicated by the pipe, 31. It is understood thatthe pipes 21. and 31 may be supplied from some common source ofcompressed air usually found in metallurgical plants.

In operation and assuming that the electrodes in the conduit, 10. and 11are to be conditioned, the set of distributing pipes in these conduitsare connected up by the reinsertion of the replaceable pipe connection,20. The receiver, 24, having been filled with air to about sixatmospheres, pressure, is allowed to exhaust itself through the mainvalve. 32, into the header system. At the same time air pressure, actingon the acid in the supply tank, forces acid therefrom through theatomizer where it is separated into extremely fine particles. The fineparticles are'conducte'd with a relatively large amount of air throughthe piping system, where it is divided approximately evenly and isdischarged from the vents, 15. onto the electrodes as an extremely finecloud-like mist. This cloud of mist passes through the electrodes, someof it adhering to them due to contact in passing. The remainder passeson out the main flue to the stack. Vhen the electrodes are barelycovered, as hereinbefore suggested, the supply of acid is cut off fromthe electrodes; the supply pipes cut off from the gas conduit, and theprecipitating action is rein-augurated and continued until the gasesleaving the treater begin to cloud with solids, at which time theprecipitating action is stopped and the electrode reconditioned.

It is understood that the method of ap-- plying the mist to the screenand wire electrodes is not necessarily confined to the proceduredescribed. It may be found more convenient, for instance, to introducethe cloud of acid mist in the chamber or conduit before the gas reachesthe electrodes, the mist being carried into contact with the electrodeswith air or gas currents.

Referring to the disclosure in Figure 2 it will be understood that theatomizing device 29 and the parts leading thcrctororrespond to thesimilarly numbered parts in Figure 1. The atomizing device dischargesinto a distributing pipe 31 which extends centrally across either thetop chamber or the bottonrchamber 32 of a gas compart ment in a wellknown form of pipe treater. The treater includes a plurality of pipes 33through which the gases rise vertically. Discharge electrodes 34 arestretched axially through the pipes. The acid distributing pipe 31 isprovided with a reduced extension 35 and both pipes 31 and 35 areprovided with downwardly-directiug discharge parts 36.

The second method. used in connection with the showing in Figure 2 isessentially like that described. It is the intent in this case to passthe cloud of mist for a few moments at intervals through the pipes,conditioning their surfaces. This is accomplished by liberating the acidmist in either the top chamber or bottom chamber of gas compartment.\Vhen it is released in the upper chamber, it is necessary to do so withthe gas excluded so that the mist may be carried down throughthe pipesby a current of air. TVhen it is released in the bottom chamber it maybe introduced iuthe gas column and conveyed to the electrodes by thismeans. It has not been found necessary to insulate the sprayingapparatus in this method. Considerable advantage is obtained in havingit grounded so that. permanent connection may be made to the outsideservice.

Having thus described my invention, I

claim 1. In the. art of electrical precipitation of suspended solidmatter from gases, the method of maintaining a metailic electrodeconductive in cases where the precipitated material is non-conductingand tends to accumulate a charge by the action of the elec: tric field,which method consists in applying directly to the face of the electrodesurface. an acid in the form of a fine/mist to form on the electrodesurface a thin layer capable of defeating any tendency of the charge toimpair the conductivity of the metallic electrode surface.

2. In the art of precipitating suspended particles from gases'byelectric action, the method of maintaining conductivity between theparticles and an impenetrable electrode surface which consists inconfining a thin film of a conducting liquid containing sulphuric acidto the electrode surface.

3. In the art of precipitating suspended particles from gases byelectric action, the method of maintaining conductivity between theparticles and the active face of the electrode surface which consists indistributing loo a thin film of sulphuric acid in finely dividedparticles over said active face.

4. In the art of precipitating suspended particles from gases byelectric action, the method of maintaining conductivity between theparticles and the electrode surface which consists in distributing afilm of sulphuric acid in the form of a fine mist over the elec- 'trodesurface.

5. In the art of precipitating suspended particles from gases byelectric action, the method of maintaining conductivity between theparticles and the electrode surface which consists in directing onto theelectrode-surface and in the absence of the gases to be precipitated aline mist of liquid constituting an electric conductor.

6. In the art of precipitating suspended particles from gases byelectric action, the method or maintaining conductivity between theparticles and the electrode surface which consists in distributing overthe electrode surface and in the absence of the gases to beprecipitated. a layer of an acid distributed in finely divided particlesconstituting an electric conductor and capable of reducing thedielectric constant of any surface film on the particles.

7. In the art of conditioning electrodes used in the precipitation or"suspended solid matter from gases, the method which con sists insubjecting the active surface of the electrode to a coating film ofsulphuric acid deposited in the form of a fine mist.

8. In the art of conditioning electrodes used in the precipitation ofsuspended solid matter from gases, the method which con sistsinintermittently subjecting the active surface of the electrode to acoating film of sulphuric acid.

9. In the art of precipitating suspended solid matter from gases byelectric action, the process which consists in spraying the electrodeswith sulphuric acid until the ac tive surfaces thereof are coated withthe acid, interrupting the acid spraying action. causing thepreclpitation of the suspended matter from the gas onto the sprayedelectrodes Without addition oft" any substance, interrupting theprecipitating action as the electrodes become free of the acid coatingand again spraying the electrodes with the acid.

10. In the art of conditioning electrodes which consists in causing amist of finely divided particles of sulphuric acid to adhere to anactive face of the electrode and thus form a thin film on the same.

11. An electrode for use in the electric precipitation of solids fromgases including a metallic conductor having a thin llOlbfiOW- ringcoating of sulphuric acid on an active face thereof.

Signed at Tacoma in the county of Pierce and State of Washington this21st day of April, A. i 1921.,

ROSS BUXTON RATHBUN.

